Over the years, various female receptacles for making electrical contact with a male plug have been developed. One type, which is especially useful as a female receptacle on an extension cord, includes an overmold which houses a pair of clothes-pin type metal female contacts and a D-shaped metal female pin. The female contacts and the female pin are typically mounted within the overmold by positioning the female contacts and the female pin in a cavity of a mold and then overmolding them with a suitable material, such as vinyl.
In operation, as the female contacts receive male pins of an associated male plug, the female contacts expand and, as a result, are urged directly against the overmold. The overmold, in turn, urges the female contacts against the male pins such that the female contacts grip the male pins. In order to provide sufficient gripping force, the overmold is typically made from a vinyl having a relatively high durometer measurement (i.e., in a range of from about 90 durometer to about 95 durometer).
The female receptacle of the type described above has numerous disadvantages compared to its wall-mounted counterpart. For instance, while the durometer measurement of the vinyl typically ranges from about 90 durometer to about 95 durometer, the overmold of the female receptacle is relatively flexible. As a result, the spacial relationship of the female contacts and the female pin may not remain fixed (i.e., they are movable relative to one another), thereby presenting the possibility that the female receptacle may fail to exert a sufficient gripping force on the male plug engaged therewith. Obviously, such a condition may have a detrimental affect on the performance characteristics and the useful operating life of the female receptacle.
It is common knowledge that the durometer measurement of vinyl varies substantially in response to a change in temperature. As a result, when a female receptacle is overmolded with a vinyl material, the insertion force and retraction force for an associated male plug may vary substantially in response to temperature changes. For instance, the rigidity of vinyl increases at low temperatures, and, as a result, insertion and retraction of a male plug into and from a vinyl overmolded female receptacle may be more difficult at such temperatures. In contrast, the flexibility of vinyl increases at high temperatures, and, as a result, a vinyl overmolded female receptacle may not exert sufficient gripping force upon a male plug at such temperatures.
A further disadvantage results from the fact that molding material can flash into the female contacts during the molding process. Such flashing may create a discontinuity between the female contacts and their corresponding male pins of a male plug, thereby creating the possibility of a short circuit.